The present invention relates to discharge lamp units used as headlights of a vehicle and so on.
With conventional discharge lamps used as headlights of a vehicle, lamp sockets are provided in respective lamp-mounting places of the vehicle and lamp-lighting circuit units each containing a high-voltage generating transformer with a control circuit assembled on a printed circuit board are separately mounted in a bonnet of the vehicle, then the lamp-lighting units are connected to the respective lamp sockets by using separate high-voltage cables.
There has been developed a compact and light-weight high-voltage generating transformer which has a coil case having an insert-formed primary coil (conducting plate) and a secondary-coil-wound bobbin with a core inserted in a hollow center thereof (as disclosed in Japanese Laid-open Patent No. 8-130127). This type of transformer, however, has a constructional deficiency that the coil case is partially opened (i.e., the secondary coil bobbin is not completely enclosed by the conductive plate).
As described above, the conventional discharge lamp unit requires separate arrangement of a lamp socket apart from the lamp lighting circuit unit and interconnection of them by using a high-voltage cable. This complicates the mounting work of the unit.
Furthermore, the use of elongated high-voltage cable may be associated with the risk of a leak current therefrom and reduction of the output voltage of the discharge lamp unit.